Reduction of spastic hypertonia during repeated passive knee movements in stroke

Objectives: To quantify changes in spastic hypertonia during repeated passive isokinetic knee movements in stroke patients and to assess the role of muscle activity. Design: A between-groups design with repeated measures. Setting: Rehabilitation center for stroke patients. Participants: Ten stroke patients with hypertonia and 10 healthy subjects matched for age and gender. Intervention: With an isokinetic apparatus, movements were imposed on the knee in series of 10 repetitions at speeds of 60degrees/s, 180degrees/s, and 300degrees/s. Main Outcome Measures: Spastic hypertonia was assessed on the basis of torque measurement and electromyographic activity of the quadriceps, hamstrings, and gastrocnemius muscles, Results: Compared with the controls, stroke patients presented a significantly stronger torque reduction during the mid- and endphases of movements at all speeds tested (P<.05). The strongest torque decline occurred during knee flexion and during the first movements. The effect increased toward the end phase of movements and with increasing speeds. The effect of movement repetitions on torque measurements was unchanged after electromyographic activity was included in the statistical analysis, except during extension movements at 180degrees/s and 300degrees/s. Conclusion: Passive movements of the knee induced a decrease of spastic hypertonia in stroke patients through a combination of reflexive and mechanical factors. The role of these mechanisms is velocity dependent and differs for flexion and extension movements.